Pendulum potentiometer



Sept. 8, 1959 L. K. DAVIS PENDULUM POTENTIOMETER Filed Sept. 11, 1943 3 Sheets-Sheet l Z W. a a u y M x mm m Z? NWWZQQW I; f i: m Q Q f x. w Ly n 5 I a w 4 N u w 9 m 4 a a w u u u n a u gi /2Z2, w. 6 &2??? 3 a 4 w u & m w 3 m Ki d 1 Lina ATTORNEY 5 Sheets-Sheet 3 U 6 8 6 5 5 s W A H R m m 9 m K m 3 M m L 9 0 a 0 M F W 8 v, L MAW F w/m 6 9 o 5 5 I I; 2 F

Sept. 8, 1959 Filed Sept. 11, 1945 United States Patent PEN DULUM POTENTIOMETER Lincoln K. Davis, Brockton, Mass, assignor to the United States of America as represented by the Secretary of the Navy Application September "11, 1943, Serial No. 502,071 12 Claims. (Cl. 33843) This invention relates to variable resistors or rheostats and more particularly to a novel device of this character in which the resistance is varied automatically in accordance with the movements of a pendulum. The new pendulum-controlled resistor is simple and rugged in construction and positive in operation.

The variable resistor of the invention may be used in various control systems wherein it is desired to provide a resistance which varies with changes in the angular position of a body with respect to a horizontal plane. For example, the invention is admirably suited for use in a depth steering system in anti-submarine torpedoes to prevent too sudden diving or ascending of the torpedo, as disclosed in a copending application of C. K. Stedman et al., Ser. No. 502,075, now abandoned, filed September 11, 1943. Accordingly, for illustrative purposes the invention will be described and illustrated in a form suitable for this use, although it is to be understood that the invention may take other forms as Well.

One object of the invention resides in the provision of a novel variable resistor comprising a resistance element and a contacting member having a curved face, the resistance element and contacting member being movable relatively to cause the curved face to roll along the resistance element with a wiping action and thereby vary the effective resistance.

Another object of the invention is to provide a variable resistor of the character described in which the contacting' member is in the form of a shoe carried by a pendulum and normally biased against the resistance element with a spring action.

A further object of the invention is to provide a variable resistor of novel construction comprising a resistance element and a pendulum pivotally mounted in eccentric relation, and a contact shoe on the pendulum having a curved face movable along the resistance with a rolling and wiping action upon movement of the parts about their respective pivots.

These and other objects of the invention may be better understood by reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of one form of the new pendulum-controlled resistor;

Fig. 2 is an enlarged view in front elevation of the device illustrated in Fig. 1, with parts removed, showing the positions of the elements when the device is tilted in one direction from its normal level position;

Fig. 3 is a sectional view on the line 3-3 in Fig. 1;

Fig. 4 is a view similar to Fig. 2 but showing the normal or level positions of the elements;

Fig. 5 is a side view partly in section on the line 5-5 in Fig. 4;

Fig. 6 [is a sectional view on the line 66 in Fig. 4;

Figs. 7 and 8 are enlarged sectional views on the lines 7--7 and 8-8, respectively, in Fig. 4;

Fig. 9 is an enlarged sectional view on the line 99 in Fig. 1;

2,903,665 Patented Sept. 8, 1959 Fig. 10 is an enlarged sectional view on the line 10--10 in Fig. 4;

Fig. 11 is an enlarged sectional view on the line 11-11 in Fig. 2;

Fig. 12 is a perspective view of the contact shoe;

Fig. 13 is a front view of part of a modified form of the new variable resistor, and

Fig. 14 is a sectional view on the line 14-14 in Fig. 13.

Referring to the drawings, the variable resistor there shown comprises a frame 20 having a pair of longitudinal members 21 disposed in parallel spaced relation and connected together near opposite ends by cross members 22. Intermediate its ends, each longitudinal member 21 is connected to a generally vertical member 23, the members 23 extending upwardly from the longitudinal members in parallel spaced relation. The frame 20 may be mounted in any suitable manner, as by connecting one of the vertical members 23 to a support 24 (Fig. 5).

A resistance element 26 is pivotally mounted on a stud 27 connected to one of the vertical members 23 of the frame near its upper end. As shown, the resistance element 26 comprises a coil of wire of any desired resistance value, for example, 20,000 ohms, the wire being coiled around a bar 2601 of insulating material. At its upper end, the bar is connected to an arm 28 movable on the pivot 27, the connection of the resistance bar to the arm being made through insulating plates 29 secured by bolts 30 extending through the plates and the adjacent ends of the arm and the bar. A terminal 31 is interposed between the resistance bar 2611 and one of the insulating plates 29 and is connected by a wire 32 to the lower end of coil 26. A similar terminal 33 on the upper end of the resistance bar is connected to the upper end of coil 26.

A shaft 35 extends through the vertical members 23 of the frame near its upper end and is held in position by nuts 36 screwed against the outer faces of the frame members. A set of ball bearings 37 is mounted in suit able raceways 38 (Fig. 3) on the shaft 35 between the frame members 23 and supports a pendulum 39. The raceways 38 are positioned axially on shaft 35 intermediate its ends by spacers 40. At its lower end, the pendulum 39 carries a bob 41 having a downwardly projecting stud 42. A nut 43 is threaded on the stud 42 and supports a collar 44 which is rotatable freely on bearings 43a between the collar and the nut. The pendulum is guided in its swinging movements by a pair of arc-shaped bars 45 connected at their ends in any suitable manner to the cross members 22, as by means of screws 46. On the upper faces of the members 22 are rubber stops 47 engageable with the bob 41 for limiting the swinging movements of the pendulum. The guide bars 45 are disposed in parallel relation on opposite sides of the collar 44 and are spaced slightly from the collar to permit a slight lateral movement of the pendulum. Since the collar 44 is rotatable freely on the bearings 43a, the friction incident to engagement of the collar with the guide bars 45 is negligible. Intermediate their ends, the guide bars 45 are connected to a cross piece 48 which serves to brace the guide bars, the cross piece being spaced from the lower faces of the bars by spacers 49.

A contact shoe 51 having a curved face 51a is mounted on the pendulum at one side thereof adjacent the resistance element 26 and is suitably insulated from the pendulum. As shown, the shoe 51 is connected to the pendulum by two arms 52 which support the shoe in spaced relation to the pendulum. The arms 52 are secured to the pendulum by transverse studs 53 and are insulated from the studs and the pendulum by suitable insulation 54 (Fig. 7).

The-contact shoe 51 and the resistance element 26 are held in alignment by a pairof plates 56 and 56a connected to opposite faces of the resistance bar 26a near itslower end, as by means of bolts 57 The plates 56 and 56a extend from the resistance bar on opposite sides of the'pendulurn 39inclosely spaced relation thereto and are connected together at their free ends by a screw 58 A tension spring 59is secured-at one end=to an ear 60 on the plate'56 and at the opposite. end to the bob 41, whereby the curved face 51a of'the contact shoe is held against the resistance element 26 with-a spring action. It will be apparent that plates 56, 56a hold the contact shoeand the resistance element in alignmentwhile permitting slight relative movement thereof incident to swinging of the pendulum.

At its upper end, the contact shoe 51 is connected by awire 62 to a terminal 63 mounted on an insulating strip Men the upper end of one of the vertical members 23 ofthe frame. A similar insulated strip 65 is mounted on the other frame member 23 and carries a terminal 66 which may be connected by a wire (not shown) to either end of the resistance element through one of the terminals 31, 33, as will be described in greater detail presently.

Assuming that it is desired to effect an increase in resistance upon movement of the pendulum to the left relative-to the frame and a decrease in resistance upon movement of the pendulum to the right relative to the frame, as seen'in Figs. 1, '2, and 4,- the upper end of resistance coil-26-is connected through terminal 33 and suitable wiring (not shown) to the terminal 66. In the normal level position of the device (Fig. 4), the'curved face of contact shoe 51 engages the resistance coil 26 intermediate its ends sothat the effective value of the resistance is approximatelyhalf its total value. It will be apparent that the resistance circuit is from the terminal 63 through wire62, shoe-51, the part of coil 26 above its point of contact with shoe 51, and terminals 33 and 66. When the pendulum swings to the right relative to the frame (Fig. 2), due to tilting of the support 24 on which the frame is mounted, the resistance element 26 swings with it and causes the curved face 51a of the shoe to roll up-- wardly along the resistance coil due to the eccentric mountingof the pivots 27 and 35 of the resistance and pendulum, respectively. As a result, the effective resistance of the coil 26 is reduced to a value corresponding to'the reduced length of that portion of the coil above its point of contact with the shoe. Conversely, when the pendulum swings to the left relative to the frame, the curved face 51aof the shoe rolls downwardly along the coil 26 so that the effective resistance of the latter is increased to a value corresponding to the increased length of that portion of the coil above its point of contact with the shoe. By reason of the eccentric mounting of the pivots 27 and 35, rolling of the contact shoe onthe resistance coil incident to swinging of the pendulum is accompanied by a slight wiping action or sliding move-- ment of the shoe relative to the coil, the spring 59 and guide 56, SSpermittingrelative movement of the contactshoe and the resistance to accommodate the rolling and sliding action. The sliding action of the contact shoe is a desirable feature of the variable resistor, since it insures good contact and tends to prevent the accumulation onthe resistance coil of foreign matter which would impair the conduction of current between the shoe and the coil,v

If it is desired to effect a decrease in the resistance upon'movement of pendulum to the left relative to the frame and an increase in resistance upon movement of the pendulum to the right relative to the frame, as seen in Figs. 1, 2 and 4, the connection of the resistance coil 26 toterminal 66 is reversed. That is, the lower end of the'coil is connected to terminal 66 through wire 32 and terminal 31.

The contact face 51a of the shoe may have any desired curve, depending upon the required relation of resistance variations to swinging movements of the pendulum. As shown, the contact face 51a is curved empirically so that the characteristic of angular displacement of the pendulum against resistance is approximately linear. The distance between the pivots 27 and 35 for the resistance and pendulum, respectively, determines the degree of the wiping action between the contact shoe and the resistance coil, which is preferably a compromise between the minimum wiping action required to maintain good contact and the maximum friction allowable without interfering seriously with the pendulum action. It will be apparent that the relatively small wiping action requires only a small amount of work from the pendulum and permits a high degree of mechanical sensitivity. With my new construction, the amount of work required to effeet a change in resistance is relatively small, in contrast with the work required to effect a corresponding resistance change in the conventional linear slide orrotary potentiometer.

The device shown in Figs. 13 and 14 is similar to that illustrated in Fig. 1 except that it may be adjusted to vary the relative positions of the pivots for the resistance and the pendulum. More particularly, in the device shown in Figs. 13 and 14, the arm 28 of resistance element 26 is mounted on a pivot 66 in a block 67 disposed between the frame members 23. The block 67, in turn, is mounted near its upper end on a pivot 68 secured to one of the frame members 23. Accordingly, the position of the resistance pivot 66 relative to the pendulum pivot 35 may be varied by swinging the block 67 on pivot 68; The block may be locked in any desired position by means of a screw 69 engageable with the pin 68. Prefer ably, an additional locking means is provided in the form of ascrew 70 extending loosely through an arcuate slot 71 in the frame member 23 and threaded in the block 67 intermediate its ends. The screw 70 is loosened to permit adjustment of the block and is then tightened to clamp the block in its adjusted position.

It will be apparent from the foregoing description that the variable resistor of my invention is simple and rugged in construction and sensitive in operation. The parts are preferably proportioned and positioned so that the region of contact between the shoe 51 and resistance 26 is offset from a line between their respective pivots 35 and 27 in all positions of the pendulum, whereby the desired wiping action is obtained throughout the range of movement of the pendulum, as described in my copending applica-' tion Ser. No. 502,070, filed September 11, 1943,

which matured into Patent 2,472,369, of which this ap plication is a continuation-in-part.

I claim:

1. A variable resistor comprising a resistance element, means pivotally suspending said resistance element, a contacting member, means spaced from said resistance element suspending means pivotally suspending said contacting member adjacent the resistance element, said the contacting member and resistance element on said suspending means to cause said member to roll and simul taneously slip along said element with a wiping action.

3. A variable resistor comprising a resistance element, a contacting member having an invariable curved surface adjacent the resistance element, an angularly shiftable bracket having means for pivotally suspending said 'mem bar 1 3 element in eccentric relation, means adapted upon angular shifting of said bracket to swing the contacting member and resistance element on said suspending means to cause said member to roll and simultaneously slip along said element with a wiping element action, and biasing means for urging said member and element together with a spring action.

4. In combination with a pendulum, a resistance element, means pivotally suspending the resistance element eccentrically of and adjacent the pendulum, and a contact shoe carried by the pendulum and having a curved face operable to roll and simultaneously slip along said element with a wiping action upon movement of the pendulum.

5. In combination with a pendulum, a resistance element, means pivotally suspending the resistance element adjacent the pendulum, a contact shoe carried by the pendulum and having a curved face engageable with said element, said means for pivotally suspending said element being eccentric to the pendulum whereby operation of the pendulum causes the shoe face to roll and simultaneously slip along said element with a wiping action.

6. In combination with a pendulum, a resistance element adjacent the pendulum, a contact shoe carried by the pendulum and having a curved face engageable with said element, separate means for pivotally mounting the pendulum and said element whereby operation of the pendulum causes the shoe face to roll along said element with a wiping action, and means for changing the relative positions of said pivotal means.

7. A variable resistor comprising a resistance element, a frame, means for pivotally mounting said element on the frame, a pendulum, means for pivotally mounting the pendulum on the frame and offset from said first pivotal means, a contact shoe on the pendulum, the shoe and said element having interengaging faces one of which is curved, and a tension spring connected between the pendulum and said element for urging said faces together, the pendulum being operable to roll and simultaneously slip said curved face along the other face with a wiping action.

8. A variable resistor comprising a resistance element, a frame, means for pivotally mounting said element on the frame, a pendulum, means for pivotally mounting the pendulum on the frame and ofli'set from said first pivotal means, a contact shoe on the pendulum, the shoe and said element having interengaging faces one of which is curved, a tension spring connected between the pendulum and said element for urging said faces together, the pendulum being movable on the frame to roll and simultaneously slip said curved face along the other face with a wiping action, and means on the frame for guiding the free end portion of the pendulum in its movement.

9. A variable resistor comprising a resistance element, a frame, means for pivotally mounting said element on the frame, a pendulum, means for pivotally mounting the pendulum on the frame and offset from said first pivotal means, a contact shoe on the pendulum, the shoe and said element having interengaging faces one of which is curved, a tension spring connected between the pendulum and said element for urging said faces together, the pendulum being movable on the frame to roll said curved face along the other face with a wiping action, and guide means movable with said element and pendulum for holding said faces in alignment.

10. A variable resistor comprising a resistance element, a frame, means for pivotally mounting said element on the frame, a pendulum, means for pivotally mounting the pendulum on the frame and offset from said first pivotal means, a contact shoe on the pendulum, the shoe and said element having interengaging faces one of which is curved, a tension spring connected between the pendulum and said element for urging said faces together, the pendulum being movable on the frame to roll and simultaneously slip said curved face along the other face with a wiping action, and stops for limiting the swinging movements of the pendulum.

11. A variable resistor comprising a resistance element, a frame, means for pivotally mounting said element on the frame, a pendulum, means for pivotally mounting the pendulum on the frame and oifset from said first pivotal means, a contact shoe on the pendulum, the shoe and said element having interengaging faces one of which is curved, means for insulating the shoe and said element from the frame, and means for connecting the shoe and one side of said element in a circuit, the pendulum being operable to roll and simultaneously slip said curved face along the other face and thereby vary the effective resistance of said element.

12. In a rheostat, a resistance member, a contact member engaging said first member, the contact member and resistance member being movable relatively to vary the effective resistance of said first member, a pendulum, and constraining means actuated by the pendulum for moving said members relatively to displace the point of contact thereof relative to one of the members a distance which is different from the distance through which the members move relatively, whereby one of the members moves along the other with a combination rolling and sliding action.

References Cited in the file of this patent UNITED STATES PATENTS 839,708 Bijur Dec. 25, 1906 1,308,043 Cook July 1, 1919 2,120,771 Thompson June 14, 1938 2,216,086 Meenan Sept. 24, 1940 2,333,477 Duston Nov. 2, 1943 FOREIGN PATENTS 234,223 Great Britain May 28, 1925 

